1. Field of the Invention
The present invention generally relates to a car rental system and, more particularly, to a car rental system in which cars are operated by digital keys instead of conventional metal keys.
2. Background Description
In a typical car rental system today, car keys are left in cars when cars are waiting to be picked up by customers or when cars are dropped off by customers at a gated parking lot. Consequently, keys are vulnerable to be stolen or copied. It is very costly to disable a stolen key-usually an authorized car dealer or locksmith needs to be involved. It is also very dangerous when a car key is copied by a malicious person who can follow the car when it exits the parking lot, and steal the car when it is unattended.
U.S. Pat. Nos. 5,289,369 to Hirshberg and 5,812,070 to Tagami et al. disclose integrated circuit (IC) card based access control methods where each car is equipped with a IC card reader which can communicate with a cental station by wireless communications. The cards in these patents store the identifications (IDs) of the renters carrying the cards. Upon being inserted into a card reader on a rental car, the ID stored in the card is read out and sent to the cental station to check for proper authorization. In case of outage of wireless communications, the system will fail to work.
U.S. Pat. No. 4,477,874 to Ikuta et al. discloses an off-line access control method based on the secret codes stored on a car and a card. Basically, a car stores two secret codes, one for master and the other for slave. A card that carries the master secret has full control of the car, whereas the card carrying the slave secret code has limited control. For example, a slave card only authorizes the driver to start the engine but not to open the trunk lid. In such a system, if the master card is lost, the car reader has to be re-programmed with a new master secret code. This system is not suitable for a rental system since the reader on the car needs to be re-programmed for every renter.